Comparative Assessment of Hydrogen and Methanol-Derived Fuel Co-Combustion for Improved Natural Gas Boiler Performance and Sustainability

Faced with a global consensus on net-zero emissions, the use of clean fuels to entirely or substantially replace traditional fuels has emerged as the industry’s primary development direction. Alcohol–hydrogen fuels, primarily based on methanol, are a renewable and sustainable energy source. This research focuses on energy sustainability and presents a boiler fuel blending system that uses methanol–hydrogen combinations. This system uses the boiler’s waste heat to catalytically decompose methanol into a gas mostly consisting of H2 and CO, which is then co-combusted with the original fuel to improve thermal efficiency and lower emissions. A comparative experimental study considering natural gas (NG) blending with hydrogen and dissociated methanol gas (DMG) was carried out in a small natural gas boiler. The results indicate that, with a controlled mixed fuel flow of 10 m3/h and an excess air coefficient of 1.2, a 10% hydrogen blending ratio maximizes the boiler’s thermal efficiency (ηt), resulting in a 3.5% increase. This ratio also results in a 1% increase in NOx emissions, a 25% decrease in HC emissions, and a 5.66% improvement in the equivalent economics (es). Meanwhile, blending DMG at 15% increases the boiler’s ηt by 3%, reduces NOx emissions by 13.8% and HC emissions by 20%, and improves the es by 8.63%. DMG, as a partial substitute for natural gas, outperforms hydrogen in various aspects. If this technology can be successfully applied and promoted, it could pave a new path for the sustainable development of energy in the boiler sector.